Tobacco bales require to be broken up or opened for processing of the tobacco into desired products. The bales are generally comparatively dry and the tobacco must be premoistened to inhibit degradation of the tobacco on bale opening.
A number of commercial systems are known for the premoistening of tobacco bales for later separation of the layers of premoistened tobacco. These are batch operations effected on a bale or a number of bales using steam as the moistening agent.
There is also one commercial continuous process described in U.S. Pat. No. 3,838,698. In this patent, there is described a method and apparatus for the continuous moistening and opening of tobacco in which a rectangular bale is constantly urged towards an opening and moistening zone and is impaled on a straight hollow probe extending in the direction of movement of the bale. The probe has openings through which vacuum is applied to draw steam provided as an ambient atmosphere in the opening and moistening zone into the front face of the bale. Rotary doffers are located in the opening and moistening zone and engage the front face of the bale to remove therefrom tobacco which is moistened by the steam. This prior art procedure is commonly termed the "Dickinson System".
In the Dickinson system, the bales are oriented with the grain located horizontally and extending from end to end and the rotary doffers are mounted for rotation about horizontal parallel axes.
The Dickinson System has the distinct advantages over the batch systems that the tobacco is opened after moistening in the same unit and the process can be stopped at any time so as to tailor the flow of treated tobacco to that desired.
The Dickinson System suffers from a number of drawbacks. For example, to operate efficiently in moistening the tobacco, a considerable vacuum must be applied to the probe, requiring a high powered motor to drive the vacuum pump, typically about 40 h.p. Small tobacco particles are drawn through the openings in the probe under the influence of the vacuum, requiring the separation of these particles from the vacuum line before entering the pump.
Another problem with the Dickinson System is that equipment is necessary to rotate the probe to prevent clogging of the openings by tobacco particles and thereby impairing the ability to apply vacuum to the interior of the block. This rotation often is insufficient to prevent clogging. Power is consumed in the Dickinson System in the effort of moving the bale forwardly against the probe.
Additionally, probe bending is sometimes observed and, if this condition is not detected and corrected soon enough, the probe may break off. Further, a vacuum seal is required around the bale, which limits the shape of tobacco bales which can be treated.